System and method for ensuring continued operation of fan notwithstanding bmc failure

ABSTRACT

A system for maintaining the operation of a cooling fan for a server if that function of a baseboard management controller (BMC) of the server should fail includes the BMC and a control module. The control module is electrically connected to the BMC and the fan, and the control module receives a first signal outputted by the BMC in a cycle and determines the state of the BMC depending on whether the first signal includes a change in level or fails to include a change in level. When an abnormal state of the BMC is determined, the control module outputs a preset pulse width modulation (PWM) signal to the fan to maintain operation of the fan. The present disclosure also provides a fan control method.

TECHNICAL FIELD

The present disclosure relates to the technical field of server, inparticular to a system and method for controlling fan.

BACKGROUND

In order to ensure the stability of the server, the server ensures thatits own fan is operating. At present, the baseboard managementcontroller (BMC) of the server applies a control method for thebaseboard management controller (BMC) to output pulse width modulation(PWM) signals to the fan to adjust the speed of the fan. However, whenBMC is working abnormally, the fan may work abnormally, or even stop,leading to overheating of the server and shut down.

Therefore, improvement is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fan control system according to anembodiment of the present disclosure.

FIG. 2 is a schematic diagram of the fan control system according toanother embodiment of the present disclosure.

FIG. 3 is a schematic diagram of the fan control system according toanother embodiment of the present disclosure.

FIG. 4 is a flowchart of a fan control method according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

The technical solutions in the embodiments of the present disclosurewill be described in conjunction with the accompanying drawings in theembodiments of the present disclosure. Obviously, the describedembodiments are part of the embodiments of the present disclosure, notall of them. Based on the embodiments of the present disclosure, allother embodiments obtained by those of ordinary skill in the art withoutcreative work shall fall within the protection scope of the presentdisclosure. The terms used in the description of the present disclosureherein are only for the purpose of describing specific embodiments andare not intended to limit the present disclosure.

In the embodiment of the present disclosure, “first”, “second” and otherterms are only used for the purpose of distinguishing betweendescriptions and cannot be understood as indicating or implying relativeimportance, or as indicating or implying order. The features defined as“first” and “second” may include one or more of the features explicitlyor implicitly. In the description of the embodiments of the presentdisclosure, the terms “exemplary” or “for example” are used as examplesor explanations. Any embodiment or design described as “exemplary” or“for example” in the embodiments of the present disclosure shall not beinterpreted as being more preferred or advantageous than otherembodiments or designs.

In the article, unless otherwise expressly specified and limited, forlocation words, the terms “above”, “below”, “upper end”, “lower end”,“lower surface”, “clockwise”, “counterclockwise”, “left”, “right” and soon indicate that the location and position relationship are based on thelocation or position relationship shown in the attached drawings, andare only for the convenience of describing this article and simplifyingthe description, rather than indicating or implying that the device orelement referred to must have a specific orientation, be constructed, orbe operated in a specific orientation, it cannot be understood aslimiting the specific scope of protection of the present disclosure.

In the article, unless otherwise expressly specified and limited, theterms “first” and “second” are only used for descriptive purposes andcannot be understood as indicating or implying relative importance orimplicitly indicating the number of technical features. Thus, “first”and “second” defining features can explicitly or implicitly include oneor more of the features.

Some embodiments of the present disclosure are described in detail belowin combination with the accompanying drawings. Without conflict, thefollowing embodiments and features in the embodiments can be combinedwith each other.

Embodiment 1

FIG. 1 illustrates a fan control system 100 in accordance with anembodiment of the present disclosure.

The fan control system 100 is used to control the operation of a fan200. The fan control system 100 can be installed in the server (notshown in the figure) to reduce the risk of fan malfunction leading toserver overheating and shutdown. The fan control system 100 includes abaseboard management controller (BMC) 10 and a control module 20 thatare electrically connected to each other. In some embodiments, thecontrol module 20 may be a controller.

The control module 20 is electrically connected between the BMC 10 andthe fan 200. The control module 20 is used to receive the first signaloutput by the BMC and determine whether the BMC 10 is in an abnormalstate according to the received first signal.

When the control module 20 detects that the BMC 10 is in an abnormalstate, the control module 20 outputs a preset pulse width modulation(PWM) signal to the fan 200 to keep the fan 200 running. When thecontrol module 20 detects that the BMC 10 is in a normal state, thecontrol module 20 controls the fan 200 to operate according to thereceived first signal.

When the control module 20 detects that the first signal, for a presetnumber of continuous cycles, is in an error state, the control module 20determines that the BMC 10 is in an abnormal state. On the contrary,when the control module 20 detects that the first signal is not in anerror state continuously within a preset number of cycles, the controlmodule 20 determines that the BMC 10 is in a normal state.

Referring to FIG. 2 , in one embodiment, the control module 20 includesa detection unit 21, a storage unit 22, and a signal selection unit 23.

The detection unit 21 is electrically connected between the BMC 10 andthe signal selection unit 23 to detect whether the first signal is in anerror state continuously within a preset number of cycles, so as tooutput the corresponding second signal to the signal selection unit 23.

The first signal output by the BMC 10 can be a dynamic PWM signal.

The dynamic PWM signal refers to the PWM signal that the BMC 10 adjustsin real time according to the temperature of the server. The error statemeans that the level state of the first signal remains unchanged.

When the level state of the first signal remains unchanged for a presetnumber of cycles, the control module 20 determines that the BMC 10 is inan abnormal state. When the control module 20 detects that the firstsignal is not in an error state continuously within a preset number ofcycles, that is, the level state of the first signal has changed atleast once in a preset number of consecutive cycles, the control module20 determines that the BMC 10 is in a normal state.

The level state of the first signal can remain unchanged, that is,either the level state of the first signal remains at high-level or thelevel state of the first signal remains at low-level.

A change in the level state of the first signal may be the first signalfalling from the high-level state to the low-level state, or the firstsignal rising from the low-level state to the high-level state.

In the embodiment of the present disclosure, each cycle is a continuousperiod of time, such as one second.

When the fan 200 is running at full speed, that is, when the fan 200 isrunning at the highest speed, the duty cycle of the first signal isslightly less than 100%, such as 99%. That is, even if the fan 200operates at full speed, the first signal used to control the fan 200 tooperate at full speed can change from high to low level at least once inthe preset cycle. The detection unit 21 can determine whether the BMC 10is in an abnormal state by detecting the absence of a change in thelevel state within a preset number of cycles in the generated firstsignal.

When the detection unit 21 detects that the first signal has not changedthe level state within a preset number of cycles (such as 5 cycles),that is, the BMC 10 is in an abnormal state, the second signal output bythe detection unit 21 is in the first level state, such as a low-levelstate. When the detection unit 21 detects that the first signal haschanged the level state within a preset number of cycles (such as 5cycles), that is, the BMC 10 is in a normal state, the second signaloutput by the detection unit 21 is in the second level state, such as ahigh-level state.

In the embodiment of the present disclosure, the storage unit 22 iselectrically connected to the signal selection unit 23, the storage unit22 is used to output a preset PWM signal to the signal selection unit23. In the embodiment of the present disclosure, the preset PWM signalis also a pulse width modulated signal.

In some embodiments, the storage unit 22 may be a register.

In the embodiment of the present disclosure, the signal selection unit23 is also directly electrically connected to the BMC 10, to receive thefirst signal. The signal selection unit 23 outputs a target PWM signaldirected to the fan 200 according to the level state of the secondsignal input by the detection unit 21 and controls the fan 200 tooperate at the speed of the target PWM. The target PWM signal is eitherthe first signal or the preset PWM signal according to the level stateof the second signal.

The signal selection unit 23 selects the first signal or the preset PWMsignal to output to the fan 200 according to the level state of thesecond signal input by the detection unit 21 to control the operation ofthe fan 200.

For example, the signal selection unit 23 includes a first inputterminal INT1, a second input terminal INT2, a third input terminalINT3, and an output terminal OUT.

The first input terminal INT1 is electrically connected to the outputterminal of the detection unit 21 for receiving the second signal. Thesecond input terminal INT2 is electrically connected to the BMC 10 forreceiving the first signal. The third input terminal INT3 iselectrically connected to the output terminal of the storage unit 22 toreceive a preset PWM signal. The output terminal OUT of the signalselection unit 23 is electrically connected to the fan 200 foroutputting a target PWM signal to the fan 200.

When the preset number of cycles is k cycles (for example, k is equal to5), and when during the k-th cycle and any cycle after that, the levelstate of the second signal received by the first input terminal INT1 ofthe signal selection unit 23 is low. That is, when the BMC 10 iscurrently in an abnormal state, the target PWM signal output by thesignal selection unit 23 is a preset PWM signal. Thereby, the fan 200operates at a preset speed upon receiving the target PWM signal.

When the preset number of cycles is k cycles (for example, k is equal to5), and when during the k-th cycle and any cycle after that, the levelstate of the second signal received by the first input terminal INT1 ofthe signal selection unit 23 is high, the target PWM signal output bythe signal selection unit 23 is the first signal. Thereby, the fan 200operates at a corresponding speed after receiving the target PWM signal.

Until the operation cycle of the fan control system 100 has reached thepreset number of cycles, that is, the level state of the second signaloutput by the detection unit 21 is high in the previous k−1 cycle of thefan control system 100, the target PWM signal output by the signalselection unit 23 is the first signal at this time.

In some embodiments, until the operation cycle of the fan control system100 has reached the preset number of cycles, that is, during theprevious k−1 cycles of the BMC 10, the duty cycle of the output firstsignal in each cycle is 99%. The fan control system 100 controls the fan200 to run at full speed in the previous k−1 cycle.

The duty cycle refers to the proportion of the effective signal time tothe total time in a cycle. For example, the effective pulse width of thefirst signal may be 1 μs. The preset period can be 4 μs, and then in thecurrent cycle, the duty cycle of the first signal is 0.25, that is, atthis time, the value of the duty cycle of the first signal is 0.25.

In the embodiment, the signal selection unit 23 is a multiplexer (MUX).

The duty cycle of the preset PWM signal output by the storage unit 22can be set by those skilled in the art according to needs. The presentdisclosure does not limit the duty cycle of the preset PWM signal.

In the embodiment, when the preset number of cycles is k cycles (forexample, k is equal to 5), the detection unit 21 determines whether theBMC 10 is in an abnormal state by determining whether there is a changein the level state of the first signal of the current cycle and theprevious k−1 cycles. When the detection unit 21 detects that the levelstate of the first signal of the current cycle and the previous k−1cycles remains unchanged, the detection unit 21 determines that the BMC10 is in an abnormal state and outputs the second signal in a low-levelstate. When the detection unit 21 detects at least one change in thelevel state of the first signal in the current cycle and the previousk−1 cycles, the detection unit 21 determines that the BMC 10 is in anormal state and outputs the second signal in a high-level state.

The control module 20 may be a complex programmable logic device (CPLD).It can be understood that in other embodiments, the control module 20can also be an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic devices,discrete gate or transistor logic devices, discrete hardware components.

In some embodiments, the fan control system 100 further includes awarning unit (not shown), such as LED lights, buzzers, voice modules,and other graphic warning modules. The warning unit is electricallyconnected to the control module 20. When the detection unit 21 detectsthat the BMC 10 is in an abnormal state, the control module 20 controlsthe warning unit to output information to technicians to make repairs.

The fan control system 100 of the embodiment of the present disclosuredetects whether the first signal output by the BMC 10 remains unchangedfor a preset number of cycles, through the detection unit 21, todetermine whether the BMC is in an abnormal state. When the detectionunit 21 detects that the BMC 10 is in an abnormal state, the controlmodule 20 outputs a preset PWM signal to control and continue the normaloperation of the fan 200, so as to ensure the heat dissipation from theserver and reduce the risk of the server shutting down due tooverheating.

Embodiment 2

FIG. 3 illustrates a fan control system 100 a in accordance with anembodiment of the present disclosure.

The fan control system 100 a includes a BMC 10 and a control module 20a.

The difference between the fan control system 100 a and the fan controlsystem 100 is that the control module 20 a also includes a signalprocessing unit 24 and a PWM signal generation unit 25. The level stateof the first signal not changing remains the error state.

In the embodiment, the first signal output by the BMC 10 is a dynamicPWM signal.

In the embodiment, the signal processing unit 24 is electricallyconnected between the BMC 10 and the signal selection unit 23 to processthe received first signal to obtain the duty cycle of the first signalin each preset cycle and generate the corresponding third signal. Thevalue of the third signal is the duty cycle value of the PWM signalcontained in the first signal.

The storage unit 22 is electrically connected to the signal selectionunit 23 for outputting a preset adjustment signal to the signalselection unit 23. In the embodiment of the present disclosure, thevalue of the preset adjustment signal is also the preset duty cyclevalue.

The signal selection unit 23 is used to select and output the thirdsignal or the preset adjustment signal to the PWM signal generation unit25 according to the state of the second signal input by the detectionunit 21, so as to control the PWM signal generation unit 25 to generatethe pulse width modulated signal. In other words, the fourth signaloutput by the signal selection unit 23 is either the third signal or itis the preset adjustment signal.

The first input terminal INT1 of the signal selection unit 23 iselectrically connected to the output terminal of the detection unit 21for receiving the second signal. The second input terminal INT2 iselectrically connected to the output terminal of the signal processingunit 24 for receiving the third signal. The third input terminal INT3 iselectrically connected to the output terminal of the storage unit 22 toreceive a preset adjustment signal. The output terminal OUT of thesignal selection unit 23 is electrically connected to the PWM signalgeneration unit 25 to output a fourth signal to the PWM signalgeneration unit 25.

The PWM signal generation unit 25 is used to receive the fourth signaloutput by the signal selection unit 23 to generate the corresponding PWMsignal, so as to control the fan 200 to operate at a speed to dissipateheat from the server. When the fourth signal received by the PWM signalgeneration unit 25 is a third signal, the PWM signal generation unit 25generates a target pulse width modulated signal according to the thirdsignal and outputs it to the fan 200. When the fourth signal received bythe PWM signal generation unit 25 is a preset adjustment signal, the PWMsignal generation unit 25 generates a preset pulse width modulationsignal according to the preset adjustment signal and outputs it to thefan 200.

In the present disclosure, the preset adjustment signal stored by thestorage unit 22 can be data containing the duty cycle value, and theduty cycle of the first signal can be extracted by the signal processingunit 24. Therefore, the number of PWM signals required by the fancontrol system 100 can be reduced, and complexity of the circuitry forthe fan control system 100 can be reduced.

Referring to FIG. 3 , in another embodiment, the first signal output bythe BMC 10 can also be an inter integrated circuit (I2C) signal, and thefirst signal contains the duty cycle value. In this embodiment, theerror state is the loss of the first signal, that is, the BMC 10 doesnot output the first signal.

I2C bus is the existing signal transmission line between the BMC 10 andcontrol module 20.

The BMC 10 does not need to output additional PWM signal, the duty cyclevalue of PWM signal is merely stored in the register, and I2C bus iselectrically connected to the register, so that the BMC 10 can outputthe first signal to the signal processing unit 24. In the embodiment,the BMC 10 does not need to set an additional PWM signal generationmodule, which can simplify the circuit structure.

In some embodiments, the BMC 10 is provided with a specific register(not shown in the figures) to output the first signal at a fixed time.

For example, in the fan control system 100 a, the BMC 10 outputs thefirst signal in a period of one second. It is understandable that whenthe BMC 10 does not output the first signal continuously within a presetnumber of cycles, it can be considered that the BMC 10 is in an abnormalstate.

The detection unit 21 is electrically connected between the BMC 10 andthe signal selection unit 23 to detect whether the BMC 10 outputs afirst signal within a preset number of consecutive cycles, to output asecond signal to the signal selection unit 23.

When the detection unit 21 detects that the BMC 10 has not output thefirst signal continuously for a preset number of cycles, such as kcycles, that is, when the BMC 10 is in an abnormal state, and thedetection unit 21 outputs the second signal in the first level state tothe signal selection unit 23. When the detection unit 21 detects thatthe first signal has not been output by the BMC 10 for at most k−1consecutive cycles, that is, when the BMC 10 is in the normal state, andthe detection unit 21 outputs the second signal in the second levelstate to the signal selection unit 23.

In the embodiment, the BMC 10 is connected to the control module 20through the I2C bus. The signal processing unit 24 is used to decode thereceived first signal based on the I2C protocol to output acorresponding third signal. It can be understood that in the embodimentof the present disclosure, the third signal is also a signal containingthe duty cycle value.

In the embodiment, the signal processing unit 24 is also provided with aspecific register (not shown in the figures) for storing the value ofthe third signal obtained from the previous cycle of processing. Whenthe BMC 10 does not output the first signal within k−1 cycles, thesignal processing unit 24 outputs the third signal processed in theprevious cycle to the second input terminal INT2 of the signal selectionunit 23, so that the signal selection unit outputs the fourth signal andcontrols the fan 200 to continue working normally.

FIG. 4 is a flowchart depicting an embodiment of a fan control method.The fan control method can be applied to the fan control system 100 asdescribed above. The fan control method can be performed by the controlmodule 20 or the control module 20 a.

Each block shown in FIG. 4 represents one or more processes, methods, orsubroutines, carried out in the example method. Furthermore, theillustrated order of blocks is illustrative only and the order of theblocks can change. Additional blocks can be added or fewer blocks may beutilized, without departing from the present disclosure. The examplemethod can begin at block 41.

At block 41, receiving a first signal input by a BMC

At block 42, determining whether the first signal is in an error statecontinuously within a preset number of cycles. If the first signal is inan error state continuously within a preset number of cycles, block 43is implement, otherwise block 44 is implement.

The error state is the error state mentioned in the above embodiments 1to 2, which will not be repeated here.

In block 42, when it is detected that the first signal is in an errorstate continuously for a preset number of cycles, it is determined thatthe BMC 10 is in an abnormal state.

At block 43, outputting a preset pulse width modulation signal to a fan.In block 42, When it is detected that the first signal is not in theerror state continuously within the preset number of cycles, it isdetermined that the BMC 10 is in a normal state.

At block 44, controlling operation of the fan according to the firstsignal.

Each functional module in each embodiment of the present disclosure canbe integrated in the same processing module, each module can existseparately, or two or more modules can be integrated in the same module.The above integrated modules can be realized in the form of hardware orhardware plus software function modules.

Those of ordinary skill in the art should realize that the aboveembodiments are only used to illustrate the present disclosure, but notto limit the present disclosure. As long as they are within theessential spirit of the present disclosure, the above embodiments areappropriately made and changes fall within the scope of protection ofthe present disclosure.

What is claimed is:
 1. A fan control system configured for controlling afan to operate and comprising: a baseboard management controller (BMC);a control module electrically connected to the BMC and the fan, andconfigured to receive a first signal outputted by the BMC and determinewhether the BMC is in an abnormal state according to the first signal;wherein when the BMC is in an abnormal state, the control module outputsa preset pulse width modulation (PWM) signal to the fan to keepcontinuous operation of the fan; and wherein when the first signal is inan error state continuously within a preset number of cycles, thecontrol module determines the BMC is in the abnormal state.
 2. The fancontrol system of claim 1, wherein when the BMC is in a normal state,the control module control module controls operation of the fanaccording to the first signal; wherein when the first signal is not inan error state continuously within a preset number of cycles, thecontrol module determines the BMC is in the normal state.
 3. The fancontrol system of claim 2, wherein the control module further comprisesa detection unit, a storage unit and a signal selection unit, thedetection unit is electrically connected between the BMC and the signalselection unit to detect whether a level state of the first signal iscontinuously in the error state within the preset number of cycles, tooutput a second signal to the signal selection unit; the storage unit iselectrically connected to the signal selection unit, the storage unit isconfigured to output the preset PWM signal to the signal selection unit;the BMC is electrically connected to the signal selection unit, thesignal selection unit is configured to output the first signal to thesignal selection unit; and the signal selection unit is electricallyconnected to the fan, and the signal selection unit selects to outputthe first signal or the preset PWM signal to the fan according to thesecond signal.
 4. The fan control system of claim 3, wherein when thedetection unit detects the BMC is in the abnormal state according to thefirst signal, the detection unit outputs the second signal, and thesecond signal is in a first level state, the signal selection unitoutputs the preset PWM signal to the fan according to the second signal;and when the detection unit detects the BMC is in the normal stateaccording to the first signal, the detection unit outputs the secondsignal, and the second signal is in a second level state, the signalselection unit outputs the first signal to the fan according to thesecond signal.
 5. The fan control system of claim 4, wherein the firstsignal is a PWM signal.
 6. The fan control system of claim 1, whereinthe error state is that level state of the first signal remainsunchanged.
 7. The fan control system of claim 1, wherein the controlmodule further comprises a detection unit, a storage unit, a signalselection unit, a signal processing unit and a PWM signal generationunit, the detection unit is electrically connected between the BMC andthe signal selection unit to detect whether a level state of the firstsignal is continuously in the error state within the preset number ofcycles, to output a second signal to the signal selection unit; thesignal processing unit is electrically connected between the BMC and thesignal selection unit, the signal processing unit is configured toprocess the first signal to obtain a duty cycle of the first signal ineach preset cycle and generate a third signal, and output the thirdsignal to the signal selection unit; the storage unit is electricallyconnected to the signal selection unit, the storage unit is configuredto output a preset adjustment signal to the signal selection unit; thesignal selection unit is also electrically connected to the PWM signalgeneration unit, and the signal selection unit selects to output thethird signal or the preset adjustment signal to the PWM signalgeneration unit according to the second signal; the PWM signalgeneration unit is electrically connected to the fan, the PWM signalgeneration unit is configured to generate a target PWM signal accordingto the third signal and outputting the target PWM signal to the fan, orthe PWM signal generation unit is configured to generate the preset PWMsignal according to the preset adjustment signal and output the presetPWM signal to the fan.
 8. The fan control system of claim 7, whereinwhen the detection unit detects the BMC is in the abnormal stateaccording to the first signal, the detection unit outputs the secondsignal, and the second signal is in a first level state, the signalselection unit outputs the preset adjustment signal to the PWM signalgeneration unit according to the second signal; and when the detectionunit detects the BMC is in the normal state according to the firstsignal, the detection unit outputs the second signal, and the secondsignal is in a second level state, the signal selection unit outputs thethird signal to the PWM signal generation unit according to the secondsignal.
 9. The fan control system of claim 8, wherein the error state isthat level state of the first signal remains unchanged, and the firstsignal is a PWM signal.
 10. The fan control system of claim 8, whereinthe BMC is electrically connected to the signal processing unit throughan integrated circuit bus, and the first signal comprises a duty cyclevalue, and the error state is loss of the first signal.
 11. A fancontrol system configured for controlling a fan to operate andcomprising: a baseboard management controller (BMC); a control moduleelectrically connected to the BMC and the fan, and configured to receivea first signal outputted by the BMC and determine whether the BMC is inan abnormal state according to the first signal; wherein the error stateis that level state of the first signal remains unchanged. wherein whenthe BMC is in an abnormal state, the control module outputs a presetpulse width modulation (PWM) signal to the fan to keep continuousoperation of the fan; and wherein when the first signal is in an errorstate continuously within a preset number of cycles, the control moduledetermines the BMC is in the abnormal state.
 12. The fan control systemof claim 11, wherein when the BMC is in a normal state, the controlmodule control module controls operation of the fan according to thefirst signal; wherein when the first signal is not in an error statecontinuously within a preset number of cycles, the control moduledetermines the BMC is in the normal state.
 13. The fan control system ofclaim 12, wherein the control module further comprises a detection unit,a storage unit and a signal selection unit, the detection unit iselectrically connected between the BMC and the signal selection unit todetect whether a level state of the first signal is continuously in theerror state within the preset number of cycles, to output a secondsignal to the signal selection unit; the storage unit is electricallyconnected to the signal selection unit, the storage unit is configuredto output the preset PWM signal to the signal selection unit; the BMC iselectrically connected to the signal selection unit, the signalselection unit is configured to output the first signal to the signalselection unit; and the signal selection unit is electrically connectedto the fan, and the signal selection unit selects to output the firstsignal or the preset PWM signal to the fan according to the secondsignal.
 14. The fan control system of claim 13, wherein when thedetection unit detects the BMC is in the abnormal state according to thefirst signal, the detection unit outputs the second signal, and thesecond signal is in a first level state, the signal selection unitoutputs the preset PWM signal to the fan according to the second signal;and when the detection unit detects the BMC is in the normal stateaccording to the first signal, the detection unit outputs the secondsignal, and the second signal is in a second level state, the signalselection unit outputs the first signal to the fan according to thesecond signal.
 15. The fan control system of claim 14, wherein the firstsignal is a PWM signal.
 16. The fan control system of claim 11, whereinthe control module further comprises a detection unit, a storage unit, asignal selection unit, a signal processing unit and a PWM signalgeneration unit, the detection unit is electrically connected betweenthe BMC and the signal selection unit to detect whether a level state ofthe first signal is continuously in the error state within the presetnumber of cycles, to output a second signal to the signal selectionunit; the signal processing unit is electrically connected between theBMC and the signal selection unit, the signal processing unit isconfigured to process the first signal to obtain a duty cycle of thefirst signal in each preset cycle and generate a third signal, andoutput the third signal to the signal selection unit; the storage unitis electrically connected to the signal selection unit, the storage unitis configured to output a preset adjustment signal to the signalselection unit; the signal selection unit is also electrically connectedto the PWM signal generation unit, and the signal selection unit selectsto output the third signal or the preset adjustment signal to the PWMsignal generation unit according to the second signal; the PWM signalgeneration unit is electrically connected to the fan, the PWM signalgeneration unit is configured to generate a target PWM signal accordingto the third signal and outputting the target PWM signal to the fan, orthe PWM signal generation unit is configured to generate the preset PWMsignal according to the preset adjustment signal and output the presetPWM signal to the fan.
 17. The fan control system of claim 16, whereinwhen the detection unit detects the BMC is in the abnormal stateaccording to the first signal, the detection unit outputs the secondsignal, and the second signal is in a first level state, the signalselection unit outputs the preset adjustment signal to the PWM signalgeneration unit according to the second signal; and when the detectionunit detects the BMC is in the normal state according to the firstsignal, the detection unit outputs the second signal, and the secondsignal is in a second level state, the signal selection unit outputs thethird signal to the PWM signal generation unit according to the secondsignal.
 18. The fan control system of claim 17, wherein the first signalis a PWM signal.
 19. The fan control system of claim 17, wherein the BMCis electrically connected to the signal processing unit through anintegrated circuit bus, and the first signal comprises a duty cyclevalue, and the error state is loss of the first signal.
 20. A fancontrol method configured for controlling a fan to operate andcomprising: receiving a first signal input by a baseboard managementcontroller (BMC); determining whether the first signal is in an errorstate continuously within a preset number of cycles; outputting a presetpulse width modulation (PWM) signal to the fan; controlling operation ofthe fan according to the first signal.